Recognition that nocturnal penile tumescence monitoring can be of assistance in diagnosing male erectile impotence has led to the development of various types of devices and techniques for conducting such monitoring. In an article entitled "A Simple and Inexpensive Transducer for Quantitative Measurements of Penile Erection During Sleep", Behavior Research Methods and Instrumentation, Volume 1, Pages 251-252, 1969, Ismet Karacan describes a mercury strain gauge transducer for measuring penile erection, the transducer being in the form of an elastomer ring. A number of devices and procedures for monitoring penile tumescence during sleep are noted and referenced in an article entitled "Sleep-Related Penile Tumescence as a Function of Age", American Journal Psychiatry, Volume 132, page 9, September 1975. Strip chart recording instruments capable of recording two traces from input signals with a single, heated pen are also known. Such an instrument is manufactured by Astro-Med, Division of Atlan-Tol Industries, Inc., West Warwick, Rhode Island.
We have discovered that a particularly clear and objective view of the part that organic causes play in male erectile impotence can be achieved by utilizing two strain gauges attached to the base and tip of the penis. Effective monitoring and recording of tumescence variations sensed by the two strain gauges is accomplished by a specially designed strip chart recorder of the single stylus, multiplexing type.